Zinc is an intracellular mineral with important enzymatic cofactor activities for cell membrane stability, DNA and RNA structure. Zinc deficiency is associated with delayed wound healing and immune dysfunction. In patietns with hematological malignancies an inverse correlation was found between disease stage and zinc level. Patients undergoing high dose chemotherapy for hematologic malignancies are predisposed to develop oral and gastrointestinal complications, in particular oral mucositis. These patients may have relative zinc deficiency, therefore oral zinc therapy may be benefical in the prevention of these complications.